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Author Topic: EFHW impedance  (Read 9295 times)
K9AXN
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« Reply #105 on: November 09, 2017, 12:09:33 PM »

Jim,

I am still confused by your discussion of current distribution along an EFHW and the resulting radiation. Let me give my perspective and perhaps that will help you to clarify/contrast your position.

I would say that the ends of the EFHW antenna will be a current minima while the center will still be a maxima. Since radiation is relative to current, the center of the antenna will have the maximum radiation. The low current at the ends of the antenna are a result of the the forward and reflected waves causing a high input impedance. The (true) radiation resistance of the antenna is still ~72 ohms in free space despite the much higher feedpoint impedance at the end of the antenna.

- Glenn W9IQ

Glen,

Thanks for the response.  I'm approaching the discussion using a CFFW antenna.  The EFHW has too many individual issues with the varying counterpoise opinions so --- I have to use a model that is balanced at the antenna otherwise this will never end.

Your assessment of surge impedance is pretty much right on.

I tried earlier to ascertain whether there was a general understanding of the part that the surge impedance of a single wire --- not transmission line played in antenna theory and function.  I asked the question; what is the formula or technique used to measure it.  Nothing --- Now I know what a vacuum is.  I knew the equation and measurement technique 50 years ago but my grey matter is a bit foggy.  I do remember the technique but would like to see that equation because it spoke to the impedance of space which dealt with the charge displacement, acceleration and compression of electron spaces,  etc.etc.

Have to begin with surge impedance of a single wire.  Only from there, can the position be developed.  Will rearticulate the position explaining each half wave to steady state.  Then I would ask you if it is understandable.

Thanks for the courteous and professional response.

Have a great day

Regards Jim
            
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K9AXN
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« Reply #106 on: November 09, 2017, 02:06:21 PM »

Is this a CFHW dipole or CFFW dipole?

It is a CFFW dipole, as shown by the text in the upper left corner of that NEC plot.

Quote
Please model the 14MHz CFFW and the 14MHz CFHW dipole and post the results.  Need to compare the two.

I have posted plots for the CFFW and CFHW already.  The 14 MHz plots for configurations with properly scaled conductors are the same as those posted earlier for those configurations.

Suggest you might want to download NEC yourself, and experiment with configurations for which you have an interest.

Thanks again, I see that now.

Regards Jim     
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G8HQP
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« Reply #107 on: November 10, 2017, 03:21:33 AM »

Quote from: K9AXN
Have to begin with surge impedance of a single wire.  Only from there, can the position be developed.
No. Antenna textbooks do not start from this. This is because it is an unfruitful way to approach an understanding of antennas.
This may lead you to believe that all the textbooks are wrong, and their authors do not really understand antennas but merely do calculus. I am not going to play any more word games with you. Good books are available. Please read them.
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K9AXN
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« Reply #108 on: November 10, 2017, 11:13:05 AM »


Quote from: K9AXN
Have to begin with surge impedance of a single wire.  Only from there, can the position be developed.
Quote from: G8HQP
No. Antenna textbooks do not start from this. This is because it is an unfruitful way to approach an understanding of antennas.

Quote from: K9AXN
You claimed to be a PhD EE.  I didn't ask you for any credentials nor do I with others.  As such, I expected you to know how to explain the surge impedance of a single wire and how it fits into the design principals of resonant antennas.  I've requested an explanation from you and you either cannot or simply refuse to acknowledge the question.  I asked for the equation and a means to measure the surge impedance of a single wire.  Without that information the impedance of a center fed full wave antenna cannot be calculated.  You simply harp that any explanation that would make sense of the issues that would be understandable by most intellectual levels is absurd --- those people simply aren't capable --- the ultimate arrogance?

Quote from: G8HQP
This may lead you to believe that all the textbooks are wrong, and their authors do not really understand antennas but merely do calculus. I am not going to play any more word games with you. Good books are available. Please read them.

I did not say nor infer any such thing.  My opinion regarding antenna texts is they generally go very lite on antenna internals.  Then to compound the educational scheme of things, CAD tools gradually bluer internal concepts. 

You have some kind of agenda.  Put me on your do not read list if it upsets you.  If you should read what I write, why not think about it then explain to me where it goes wrong --- don't be indignant and scream your a PhD EE and we should listen without question.  Answer the questions posted with an explanation.

Titles do not impress me --- too many manufacture them hoping to exploit influence.  The world didn't pass you by --- you allowed it to do so.

Have a good day

Regards Jim
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KM1H
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« Reply #109 on: November 10, 2017, 11:40:35 AM »

Quote
Suggest you might want to download NEC yourself, and experiment with configurations for which you have an interest.

He wont since it will no longer give him a platform to impress himself. Sad but SOP over the years on several forums.
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K9AXN
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« Reply #110 on: November 10, 2017, 04:47:38 PM »

Quote
Suggest you might want to download NEC yourself, and experiment with configurations for which you have an interest.

He wont since it will no longer give him a platform to impress himself. Sad but SOP over the years on several forums.

I will finish the narrative without regard for what is said.

see ya down the road partner.

Have a great evening.  Regards Jim   
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W9IQ
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« Reply #111 on: November 10, 2017, 06:25:32 PM »

Jim,

Quote
I'm approaching the discussion using a CFFW antenna.

Thanks for clarifying that. Somehow I missed that point.

Quote
Have to begin with surge impedance of a single wire.  Only from there, can the position be developed.

It isn't clear to me how you then derive other critical pieces of information, such as radiation resistance, starting from surge impedance. Can you explain a bit more? In this case I would prefer general formulas (algebraic or calculus) you would use rather than actual examples.

- Glenn W9IQ

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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
G8HQP
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Posts: 595




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« Reply #112 on: November 11, 2017, 03:27:46 AM »

Quote from: K9AXN
don't be indignant and scream your a PhD EE and we should listen without question.
Quote from: K9AXN
I didn't ask you for any credentials nor do I with others.
On the contrary, you asked me about my "intellectual level"; I simply replied. I also said that truth is truth, whoever says it. I do not urge you (and others) to listen to me; I urge you to read the standard textbooks.

Quote
Titles do not impress me --- too many manufacture them hoping to exploit influence.
My qualifications were granted after due study and/or research by proper UK universities. I remind you that I was simply answering your somewhat impertinent question. Citing qualifications seemed to be the best way to answer; if I simply said "I am fairly clever" that would sound both vague and arrogant.

Quote
I've requested an explanation from you and you either cannot or simply refuse to acknowledge the question.  I asked for the equation and a means to measure the surge impedance of a single wire.
As I keep saying, an antenna wire does not have a surge impedance. Hence it cannot be calculated or measured. It has an average surge impedance (because surge impedance varies along the length of the wire) and a formula for estimating this can be found in some textbooks. If your understanding of antennas is based on the false assumption that the surge impedance is constant then you will mislead yourself. Surge impedance will not let you calculate radiation resistance, so is not fundamental to understanding antennas.

Quote
My opinion regarding antenna texts is they generally go very lite on antenna internals.
Why not write a better book yourself, if you believe that the existing textbooks are inadequate.
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K9AXN
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« Reply #113 on: November 11, 2017, 09:42:19 AM »

Jim,

Quote
I'm approaching the discussion using a CFFW antenna.

Thanks for clarifying that. Somehow I missed that point.

Quote
Have to begin with surge impedance of a single wire.  Only from there, can the position be developed.

It isn't clear to me how you then derive other critical pieces of information, such as radiation resistance, starting from surge impedance. Can you explain a bit more? In this case I would prefer general formulas (algebraic or calculus) you would use rather than actual examples.

- Glenn W9IQ



Glen,

I'll explain my position with the math and experiments to verify the positions shortly.  Have to finish one conversation then proceed from square one.

You appear to be quite open minded and may be able to articulate concepts better than myself.  Seems it would be easier if we start with distinguishing the different properties of electron flow and electric field displacement in a conductor. 

When you were in the wave theory section in Physics did you use the Newton's Cradle to help visualize the distinction?  If you did can you wrap words around the concept without using a video clip?  Let me know  --- I can write it up but some people are better at explanations than me.

That lecture and a few lab experiments will go a long way to prove that a single wire does have a specific surge impedance based on wire size.

From there it will be easier to wrap the math and words around my stated position regarding antenna internals.

Thanks for the courteous dialogue.

Regards Jim
           
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K9AXN
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« Reply #114 on: November 11, 2017, 10:16:49 AM »


Don't be indignant and scream your a PhD EE and we should listen without question.
I didn't ask you for any credentials nor do I with others.

Quote from: G8HQP
On the contrary, you asked me about my "intellectual level"; I simply replied. I also said that truth is truth, whoever says it. I do not urge you (and others) to listen to me; I urge you to read the standard textbooks.

Please refer to post #74, you will find your PhD EE claim --- that was prior to my query which was based on your inability to explain concepts.

Titles do not impress me --- too many manufacture them hoping to exploit influence.

Quote from: G8HQP
My qualifications were granted after due study and/or research by proper UK universities. I remind you that I was simply answering your somewhat impertinent question. Citing qualifications seemed to be the best way to answer; if I simply said "I am fairly clever" that would sound both vague and arrogant.

I've requested explanations from you and you either cannot or simply refuse to acknowledge the question.  I asked for the equation and a means to measure the surge impedance of a single wire.  You claim there is no such thing only an average.  Is that true in a NON Resonant antenna terminated with approximately 600 ohms depending on wire size?  Explain!

Quote from: G8HQP
As I keep saying, an antenna wire does not have a surge impedance. Hence it cannot be calculated or measured. It has an average surge impedance (because surge impedance varies along the length of the wire) and a formula for estimating this can be found in some textbooks. If your understanding of antennas is based on the false assumption that the surge impedance is constant then you will mislead yourself. Surge impedance will not let you calculate radiation resistance, so is not fundamental to understanding antennas.

My opinion regarding antenna texts is they generally go very lite on antenna internals.

Quote from: G8HQP
Why not write a better book yourself, if you believe that the existing textbooks are inadequate.

That's why I posted the content that you see.

If this upsets you, don't read it.  It is apparent you simply wish to poison the thread. 

Let me finish the explanations then say what you wish.  Let others decide what to believe. 

Regards Jim
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G8HQP
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Posts: 595




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« Reply #115 on: November 12, 2017, 01:36:57 PM »

Quote from: K9AXN
I've requested explanations from you and you either cannot or simply refuse to acknowledge the question.
Your question is of the form "please explain why the sky is green". The only sensible answer to that question is "the sky is not green". That is the answer I have given.

Quote
Please refer to post #74, you will find your PhD EE claim
It is not a "claim", it is a fact.

Quote
that was prior to my query which was based on your inability to explain concepts.
It seems normal in education these days that the teacher gets the blame if the student fails to learn, even when the teacher keeps referring the student to the standard textbooks.

Quote
If this upsets you, don't read it.  It is apparent you simply wish to poison the thread.
Your attitude upsets me. Your errors in understanding are merely something else to be corrected. I wish to drag the thread back to standard accepted antenna theory, based on sound science, as understood by some of the other participants. If you don't like reading what I write, then all you need to do is refer to the textbooks I have already mentioned. If you feel they are inadequate then it is up to you to show this; thus far you have failed to do so but merely spread confusion and false claims (such as radiation not coming mainly from current maxima).
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K9AXN
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« Reply #116 on: November 13, 2017, 08:12:49 AM »

Quote from: K9AXN
I've requested explanations from you and you either cannot or simply refuse to acknowledge the question.
Quote from: G8HQP
Your question is of the form "please explain why the sky is green". The only sensible answer to that question is "the sky is not green". That is the answer I have given.

I live in the Chicago area, I could not have asked why the sky is green ---- I might have asked why it's grey but not green.  

I asked a simple question of you which is basic to the design and understanding of antenna theory:  Explain the approximate surge impedance of a single wire, how it's used in antenna calculations, and how it is measured.  Answer the question and all conflict is assuaged.  No need to become upset.

I have to move on my friend, have to finish what I started.  The rest will be on the web site.  Thanks for the replies and interesting conversation.

Have a pleasant day.

Regards Jim

      

« Last Edit: November 13, 2017, 08:17:28 AM by K9AXN » Logged
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